Effects of chronic β‐blockade on rest and exercise hemodynamics in mitral stenosi

β‐blocker therapy for mitral stenosis is controversial. This study compares right and left heart hemodynamics at rest and supine submaximal exercise in patients (n = 7) receiving chronic β‐antagonists with untreated patients (n = 17) matched for age (mean ± SD = 51 ± 12 years) and valve area (0.7 ± 0.2 cm²/m²). Little benefit was observed with treatment at rest. Although pulmonary capillary wedge pressures (PCWP) were lower during exercise in the β‐blocker group (22±4 vs. 31 ± 9 mmHg; P>0.05), exercise performance was not enhanced and cardiac output response during exercise was reduced (control = 41% increase vs. 12% for β‐blockade). PCWP rose rapidly when diastolic filling periods were >300 msec in both groups. Pulmonary capillary wedge pressure was found to be a nonlinear functions (P<0.001) of diastolic filling period (PCWP = 15.9 + 5.84 × 10⁵/dfp²). These data suggest that there is a critical heart rate in patients with mitral stenosis above which hemodynamic compromise rapidly occurs. © 1995 Wiley‐Liss, Inc.